WASHINGTON — The Republican Party’s official verdict is in: Mitt Romney’s campaign lacked the right message, his preparation was weak, his campaign structure and tactics were flawed, and his use of technology was behind the times.

The Republican National Committee report released Monday explains how the party’s nominee squandered an opportunity to seize the White House from a Democratic incumbent weakened by a tepid economy and stubborn voter discontent.

Its analysis indelibly sets the legacy of Romney’s 2012 election as a mission marred by multiple strategic and structural blunders — a striking critique for the candidate who ran on his private-sector managerial expertise. Even in passages that do not mention Romney by name, the 100-page report implicitly rebukes his shortcomings.

“There’s no one reason we lost,” Reince Priebus, chairman of the Republican Party, said at the National Press Club as he unveiled the 100-page autopsy. “Our message was weak; our ground game was insufficient; we weren’t inclusive; we were behind in both data and digital; our primary and debate process needed improvement.

“So, there’s no one solution,” he added. “There’s a long list of them.”

The report covered more territory than just Romney’s campaign, with a soul-searching look at problems facing the Republican Party. The bottom line: The GOP needs to appeal to the middle-class and a broader range of demographic groups.

To reach that conclusion, it delved deeply into the difficulties the former Massachusetts governor encountered as he attempted to compete with President Obama’s operation and found himself outgunned in terms of political message, demographic appeal, and ground-level operations.

The report was the result of surveying and speaking to 50,000 people who participated in focus groups. It also included conversations with political consultants and was overseen by a five-member team of co-chairs.

It does make some policy suggestions, such as an endorsement of comprehensive immigration reform. But the main thrust is on the party’s need to sharpen its message and work harder to connect with voters.

“I think our policies are sound,” Priebus said. “But I think in many ways the way we communicate can be a real problem.”

Romney himself was interviewed on a conference call for the report, and many of his top advisers were consulted. One former adviser said on Monday that he had no problems with its conclusions, even though some were blunt about Romney’s weaknesses.

“It’s like after debates, Romney never wanted to hear about what he did right,” said the adviser, who spoke on the condition of anonymity. “You should always focus on what can be improved on. Isn’t that the point? It’s not about what you can do right. It should be about what you can do better.

“They’re not scapegoating here,” the adviser added. ”But you have to look at it and say, ‘Look we could have done this better, we should have done that better.’”

Henry Barbour, a cochairman of the committee that wrote the report, said it was not meant to single out Romney and they deliberately tried not to point fingers.

“The struggles that the Republican Party are going through right now have been coming along the last several years,” said Barbour, who is also a Republican National Committee member from Mississippi. “These are not things specific to Mitt Romney. There are certainly things we learned from that campaign, some good, some bad.”

Romney’s name came up 21 times in the report, which noted that his team fell short in Hispanic outreach, was unable to win over single women voters, and lost voters under 30 by a ratio of almost 3-to-1.

Romney’s own negatives apparently compounded image problems the Republican Party must strive to correct.

“Focus groups described our party as ‘narrow-minded,’ ‘out of touch,’ and ‘stuffy old men,’” Priebus said on Monday. “The perception that we’re the party of the rich continues to grow.”

Priebus did not mention Romney by name during his prepared remarks, but the implied message was clear. The former Massachusetts governor was repeatedly cast during his campaign — by both Republicans in the primary and by Democrats in the general election — as being an out-of-touch businessman who was callous in his business dealings and a 1950s throwback in his language and his social views.

It was a viewpoint that those close to him rebutted as inaccurate and incomplete, but Romney himself later conceded that he failed to show voters a personal, more human side.

Still, not all of Romney’s struggles were his fault. The report points out that the primary process was lengthy and bitter, which damaged the eventual nominee.

Romney’s primary rivals accused him of “looting’’ companies and being a “vulture capitalist” during his tenure as chief executive of Bain Capital, laying the foundation for Obama to pursue a similar line of attack.

The party’s report asserts a shorter primary season could fix that, with 10-12 debates, which would cut in half the number from 2012. The report also wants the convention to be held in June or July instead of August or September, which would provide earlier access to general election fund-raising money.

To encourage more voters to participate, the RNC report also discourages conventions and party caucuses — like the one in Iowa, which kicks off the nominating process — and holding primaries instead, where all voters cast a ballot. Those changes would benefit a candidate like Romney, who entered the race with financial resources and front-runner status.

Reflecting the ongoing angst within the Republican Party, some conservatives on Monday criticized the party for what they saw as trying to game the system and consolidate power.

“Look at what these focus groups have got these poor guys believing. Look at this, ‘Our party’s narrow-minded,’ ” Rush Limbaugh said on his radio show Monday, after the report was released. “Out of touch? Not out of touch. We are in touch with the founding of this country. We are in touch with the greatness in this country and its people.”

To counteract the idea that “the party is seen as old and detached from pop culture” the authors propose an “RNC Celebrity Task Force” that would be made up of “personalities in the entertainment industry” who could help host events and attract younger voters. They also suggest a summit held in April to review different polling techniques and launching a program to recruit college students who can become “data, digital, and tech ‘fellows.’”

One of the few positives — which the RNC hopes to replicate — was Romney’s fund-raising, “one of the hidden gems in 2012,” the report said.

Among the other findings in the report:

■ The Obama campaign knocked on twice as many doors.

■ Romney’s paid broadcast and Internet advertising campaign devoted too few resources to securing lower rates for television ads and making sure potential voters were targeted.

■ Obama defined Romney early, and Romney never fully countered — or recovered. “The sound of silence from our side in response to the damaging attacks must never happen again,” the report read.

“If the first step of recovery is publicly admitting you have a problem,” said Fergus Cullen, a former chairman of the New Hampshire Republican Party who still has a Romney bumper sticker on his car, “then I think this accomplishes that.”